Date of Graduation

Summer 2010


Master of Science in Biology



Committee Chair

Kyoungtae Kim


endocytosis, recycling, Tlg1p, TGN, vesicles, Vps1p, Ypt32p

Subject Categories



Endocytic recycling is the process by which cells recycle endocytic materials from the trans-Golgi network or endosome back to the cell membrane, as opposed to being targeted to the vacuole for degradation. Ypt31p and Ypt32p GTPases are known to regulate the function of F-box protein Rcy1p, which mediates recycling of the plasma membrane v-SNARE Snc1p. Tlg1p and Tlg2p t-SNARE's are required for efficient endocytosis and mediate fusion of endosome derived vesicles with the late Golgi body. The dynamin-like GTPase Vps1p is required for vacuolar sorting and the late Golgi-retention of some proteins. It is known that the endocytic trafficking defect caused by the loss of VPS1 is essentially identical to cells that had lost RCY1. I hypothesized that VPS1 might play a role in recycling, along with known recycling factors including YPT31, YPT32, TLG1, and TLG2. To test this possibility, we created a number of double mutants lacking both VPS1 and its presumable functional partners. First, we checked the potential growth defects of double mutants and found that double mutants exhibited similar growth rates as single mutant cells. Whether the inactivation of VPS1 and the recycling genes together could result in defects of endocytic recycling to the membrane, FM4-64 dye, an endocytic vesicle marker, was used for visualization. We found that almost all double mutant cells accumulated dye in stages similar to vps1∆ cells. However, the rate at which FM4-64 was recycled out of the cell was found to be slower in ypt32∆vps1∆ and tlg1∆vps1∆ compared with wild type and single mutant cells. In this study, we observed that YPT32 and TLG1 share a functional redundancy with VPS1 in recycling. The investigation between VPS1 and other recycling GTPases will provide an insight into the extent of VPS1's role in endocytic recycling.


© Christopher Michael Berg

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